Creative thinking as a 21st century skill is fundamental to human development and a catalyst for innovation. Researchers frequently study it as it encourages students to analyze, synthesize, and evaluate information from different angles, vital for making informed decisions and solving complex problems. Therefore, this study aimed to assess the impact of a STEM-based curriculum on the development of creative thinking in high school students studying physics. Employing a quasi-experimental design, data were collected from 94 high school students of mixed gender and grade levels using the Torrance Tests of Creative Thinking (TTCT). Data analyses involve multivariance analyses (MANOVA) to answer the research questions. The findings showed that a STEM-based curriculum significantly impacted the development of students’ creative thinking compared to students who studied under a traditional curriculum regarding the metrics of fluency, flexibility, and originality. However, the development of participants’ metric of elaboration remained the same. Furthermore, the findings showed a significant influence of the grade level of participants who studied under a STEM-based curriculum on the metrics of fluency and elaboration. On the other hand, the findings revealed that grade level did not relate to the STEM-based curriculum for the metrics of flexibility and originality. The findings are discussed in light of recent research on the impact of STEM education.